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Old Dec 19, 2011, 04:29 PM
Fournier RF4D N1771 Awesome!
jb92563's Avatar
Riverside, CA
Joined Nov 2004
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Lazair pilot/former owner

Hey Bob,

Found this thread via the EAA video "Classic Voices" section.

I lusted after the Lazair when I was 15 and saw it at a Toronto Ultralight show.

I tried to figure out how I could own one, but a 15 it was out of my reach back then.

In 2005, living in California now I found one listed for sale in Arizona, so bought it and brought it home.

I recovered it with Tedlar and flew it for a few years at El Mirage Dry lake in CA.

Interesting thing about the aerodynamics, one early morning I took it up for a 20 minute flight and discovered upon landing that the top surface from about 25% chord on back to the TE it still had some dew on it.

It surprised me as the dew drops had not streamed or moved back but stayed in place as if totally sheltered from the airflow.

Very fun airplane to fly except when the desert thermals start to kick up as
being such a light, large wing area ultralight you moves in unison with the air and fighting the bumps is mostly futile.

I Fly full size Gliders and Motor Gliders now, but enjoyed my time in the Lazair.

Interestingly our paths have crossed unknowingly many times.

Ultralight shows in the 80's

I got my Glider license as SOSA Soaring while there from 1994-1999.

Met Ed Sweeney a few years back, and own Sean Sweeney's Fournier RF4D now. Sold Eric Sweeney my Moni.

In any case loved your video interview on EAA site and if you need logistics support for your X-country flight I'm in southern California and will lend a hand if you need some help.

I'll have to browse this entire blog to see what you have done. Sounds cool!

Ray
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Old Dec 25, 2011, 10:25 PM
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nice
wonderful
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Old Dec 26, 2011, 03:33 PM
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I'm still playing with a design model in CFD - it now has some washout & a reasonable looking taper on the main wing (+ a tiny bit of dihedral) & I thought I'd stick some winglets on - just flat 3mm sheets - the CFD is now saying 550lbs of lift at 40mph with drag around 175N - that's just 3.162kW power (neglecting inefficiency of prop, motor, controller & batteries...)
Oh yes, I've sat the pilot inside a seaplane float - that may have reduced drag a bit. The winglets have been surprisingly efficient in suppressing the wingtip vortices (considering I just plonked something on there...)
Maybe I'll post a picture again....
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Old Dec 27, 2011, 03:39 AM
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Yes please bobco i am interesting in seeing your development
Maybe you should start a new thread to share it with us?

This is one incredible thread

I have enjoyed it immensly

Many thanks to mr Kramer for allowing us all to join him on his adventure.

Ben
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Old Dec 27, 2011, 08:53 AM
homo ludens modellisticus
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The Netherlands, GE, Nijmegen
Joined Feb 2001
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10kW Scorpion motor available in Januari
http://www.scorpionsystem.com
.
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Old Dec 27, 2011, 10:02 AM
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Hi Ben,
I'm not sure where to go with it to be honest - I put it on here 'cos I was interested to hear where the original poster would go if he were starting "from scratch" today, and it's an interesting demonstration of what is available FOC to the world via the internet. There is a lot to love about the Lazair even though it's 30 years old & what everybody has said about it being the "ultimate beach toy" etc all adds to its appeal.
Today, instead of selling a kit of parts to make such a plane, you could publish, open source, a set of dxf files which anybody could take round to their local laser cutting firm - you'd get the same plane but with no delivery costs or overheads or manufacturing insurance costs (if you sell a kit that kills someone, you're liable - give away some dxf's that you make no claims for..? different story?). That's the way I was thinking of going, but my timescale is 10 years or more (would include me learning to fly....).
I'm an electrical engineer - I've designed cars (national championship winning electric cars in fact!!!) but know little of aeroplane design. However - history tells us it is relatively easy to get airborne, the tricky bit is staying alive after that.... ;^) (the wright bro's major contribution to flight was 3 axis control - lots of guys found to their cost that they could relatively easily get airborne...) - so although designing and building an electric plane is exactly my kinda project - I would need input from someone who knows something about the game.
Here's a picture anyway - I'll stop littering this excellent and inspiring thread with my witterings. If the seaplane float looks archaic, it's because that's the only design I could find on the net....

ps L/d is now 14 - getting better ;^)
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Old Dec 27, 2011, 12:09 PM
homo ludens modellisticus
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Quote:
Originally Posted by Brian Steele View Post
Edit
Quote:
Originally Posted by Brian Steele View Post
Edit.
Were have Brian's large posts gone?

Vriendelijke groeten Ron
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Old Dec 27, 2011, 01:07 PM
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Just a question ? On twins if you loose power on one engine / motor you usually have major trim problems . Wouldn't a tractor - pusher be a safer bet ?? ENJOY !!! RED
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Old Dec 28, 2011, 05:59 PM
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Flying the Lazair or any twin when you have an engine failure the aircraft will yaw towards the dead engine. To counteract the affect you have to use opposite rudder. Also a small amount of down aileron is added on the live side to keep level. This all adds drag to the power loss and hopefully the remaining horsepower will enough to keep in the air. The Lazair with the Rotax 185cc engines can do the job if the pilot weight is reasonable. I have the Pioneer 100cc version 75kg empty and a pilot weight 65kg and i end up with a slow decent. Losing an engine in flight is not a real drama but on takeoff it is a definate abort.
Ozzie
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Old Dec 29, 2011, 11:39 AM
Dale
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Year end update

The electric Lazair has about 80 hrs of flight time on it and has been flown by 16 different people.

The airplane is currently having a battery system overhaul and will be out of service for a few months.

I have decided to stop flying with the Zippy batteries at this time for several reasons:
  1. The pack capacities have degraded to about 75% of their original values due to a few weak cells out of the 384 cell total.
  2. A few Zippy cells developed pinhole vents and had to be replaced.
  3. Time consuming and difficult weak/defective cell replacement mechanism.
  4. A construction error I made by not conformal coating the battery tray circuit boards after the parts were soldered on and before I put hot melt (insulating) glue on the PCB solder connections. This error is now requiring that, if the plane was not to be flown for a couple days, all 96 4s Zippy batteries be unplugged from the PCB boards to prevent potential cell discharges due to corrosion that could develop between PCB balance pin pads. This process takes about 20 minutes to unplug them all and 40 minutes to plug them back in. Cell discharges can lead to fire.

Design considerations to take to the next battery system:
  1. Zippy cells are not consistent in quality and I will not use them again in a full scale aircraft. The issues I saw could lead to a fire. I am however, still happy with the results that I achieved. I just do not want to keep tempting fate with the known history of the cells that I have.
  2. The building block of all future packs will be individual cells, if that means having to disassemble series connected packs to obtain the cells, so be it. The cells will be assembled into parallel rows to obtain the capacity needed and then these parallel rows will be series connected together to get the needed voltage. Each cell will either be plug in or mechanically connected to its row for easy replacement.
  3. Simplify the battery to controller connection to go flying. This will involve a 200 amp power relay with a low current draw coil for each motor.
  4. Individual cell voltage monitoring and display in the air.
  5. A 'LOW cell voltage' warning light for each motor. This light would come on based on the cell with the lowest voltage and be set high enough to provide about 5 minutes of continued flying at cruise power.
  6. Automatic battery disconnect from all current drawing devices if a switch is accidentally left on or the chargers have been connected for longer than their normal charging time.
  7. Automatic battery disconnect if an individual cell goes below or above the safe cell voltage limits.
  8. Have one plug per wing/motor for connection and disconnection of the battery chargers.

I am sure that you have noticed that all these changes point towards a system that could be operated without thinking too much. I am the first to admit that the Zippy system design that I started with had to be operated by a knowledgeable and well trained 'battery' expert.

So, yes I am hoping that after successfully developing this next power system, I will become involved in the series production and sale of my electric Lazair.

In the spirit of the continued open development I have had to date, I will post here when I have made significant advances to the project in a way that may help others electrify their dream.

So in that vein, I have decided to seek 20 ampHr Li[NiCoMn]O2 cells made by EIG. I have attached their datasheet below. If any of you have a source of supply for these cells please let me know. The research I have done shows that they are very hard to obtain but would be worth the effort.

Also, I have attached a functional draft of a battery system idea that incorporates the above considerations and would appreciate any constructive criticism.

This is a system for one motor, there would be a duplicate system for the other motor.

Basically, there are two EIG 8s3p packs in series with an electrically operated 200 amp relay between them (RLY1). Each pack has latching cell level LVC and HVC's (Low and High voltage cutoffs) and a 'Reset/60 second bypass' set of contacts.

The concept is now to use a standard keyed ignition switch with a 'RUN' position and a momentary 'START' position.

Initially, when you move from OFF to RUN, nothing happens. When you continue to the 'START' position, as in starting a car, RLY1 relay is energized which powers up the motor controller, turns on the CellLog displays and turns on a 5 volt power supply that begins a 4 hour (maybe 8 hr is a better number) timer that holds RLY1 on until it times out.

And, the START position also clears all LVC and HVC cell faults (low and high voltage cutoffs) and disregards LVC and HVC faults for 60 seconds.

And, the START position also resets the 4 hour timer to zero so that you effectively get 4 hours from the last 'START' event.

I have split the current draw for all this to happen between the two 8s3p packs as equally as I can. The current draw without the LOW volts warning light on would be about 0.066 amps for the 'high' side battery and 0.034 amps for the 'low' side battery.

I have spare regulated 12 volt capacity on the 'high' side battery and spare regulated 5 volt capacity on the 'low' side battery.

When the timer times out or a LVC/HVC fault occurs, RLY1 would denergize and there would then be no current draw from either battery and the motor would obviously 'run out of gas' so to speak.

And, if you forget and leave the key in the run position, the batteries will only lose about 1/1000 of their capacity in the, up to 4 hours of unattended time. This timeout gives us a final safety feature for doing an unattended charge in addition to the cell level HVC's.

Dale
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Old Dec 29, 2011, 04:52 PM
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Hi Dale, I'll make a couple of notes & suggestions (as I feel very much on firmer ground with electrics than aeronautics.. ;^)
Lipoly fires - my impression was that the incidence of these was VERY much lower now than with batteries from just a couple of years ago. Over discharge causes a "puffy" cell rather than fire, I believe overcharging is more dangerous, but here the charger is in control.... (I recently electrified an old mountain bike & in the course of that development tried & failed to cause a LiPo fire, including attacking the pack with an axe...).
Use of relays/contacters - they are unreliable and inefficient,- I'd be tempted to use big MOSFETs instead with something like the FIA switch off a car as the final failsafe control; (you have a couple of relays in series carrying full amps). For simply switching 'on' a hundred amps or so you probably wouldn't even need a heatsink.
I sort of worry about the entire notion of trying to make the system "idiot proof", mainly because idiots are so innovative when you challenge them in this way. Also is it really the right thing to have the system cut electric power with no chance of pilot override when it thinks the batteries are empty? Shouldn't this be a choice the pilot makes? (I appreciate when a gas tank empties the pilot does not have a choice....). I guess I'm just thinking overall that anyone who's piloting or looking after an electric 'plane needs to know about its electrics - and "idiot proofing" the system is likely to add more unreliability than safety.
Those cellogs are great aren't they - the only issue I have is that the fault output plug/socket has always broken when I've tried to use it (I always ended up with a soldered connection...)
On my bike I generally "bulk charge" and do a balance charge every 4 or 5 charges. It stays balanced fine after 20 cycles or so,- v. interesting that your bigger system is stymied by the odd duff cell. An alternative approach would be to continue to use the RC LiPos but spend more on cellogs (see PS below...) - if you monitor each cell it should make finding bad ones easier - I suspect the RC cells are considerably cheaper than any of the alternatives.
Probably not much use to you; all the best anyway - I look forward to developments in 2012!
Bob
PS - you have, I guess 60 cycles on the batteries now - you say "just a few" of the ~400 cells are down to as low as 75% capacity; how many is just a few?
If you parallel cells, won't it become more difficult to spot a low capacity one? (compared to paralleling 3 full voltage series strings) Surely you'd parallel at the cell level in order to tolerate the odd low capacity cell, rather than isolate & replace it??
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Old Dec 29, 2011, 05:34 PM
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Excellent points Dale.

I also would be very cautious about using "hobby" cells in a full-scale aircraft. Who knows if Hobby King would even condone or allow the use of their cells in such a manner (commercially). The EIG cells you reference are a "safety chemistry" and boast excellent energy and power density, and have amazing cycle life as well. I honestly cannot think of a better cell for your application.

Also I can't imagine a truly big difference between fets and contactors in this application. Though going all solid-state is a bit more elegant. One thing you really want to pay attention to is quiescent current draw of your BMS systems. Make sure it is very low or can be completely disconnect from the cells, or else you may end up with a Battery Murdering System. Even months of "stand-by" is not enough, people cannot be trusted to keep their systems topped up and maintained. Somebody will run their pack flat, stick it in the hangar for a year and then get pissed when it doesn't work anymore...

I'm not sure I agree with bobc0s statement ""idiot proofing" the system is likely to add more unreliability than safety." Especially if this is indeed a prototype for a commercially viable aircraft, it had better be idiot proof, 'cause they'll do their darnedest to break your systems in new and un-imaginable ways.

I can't wait to see a finished product on the market. I would drop $20k-$30k on a kit or partially assembled plane in a heartbeat. GA is slowly dieing, who knows, this might just be the kick-in-the-shorts it needs. I know it's sure got me and a lot of others fired up

Best of luck!
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Old Dec 29, 2011, 06:22 PM
Oleg Golovidov
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Dale, any concerns or complaints about the motors or controllers?
Are you planning to stay with Joby?

If there was a way to monitor ALL cells and pinpoint bad cells, in order to replace them with fresh ones, wouldn't RC hobby batteries still be a viable implementation? likely the cheapest I would guess. But the BMS cost and complexity might become very high.
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Old Dec 30, 2011, 02:28 PM
Dale
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Quote:
Originally Posted by bobc0 View Post
(you have a couple of relays in series carrying full amps).
Actually, there is only one contact in one relay that carries full amps, that is the contact that is labeled 200a in RLY1. I think the beauty of this design is just that, a single contact is all that is needed to cut off the motor in a low voltage situation and also both chargers in a high voltage situation. If I remember correctly, when I took apart a Prius battery pack, there was a mechanical contactor in it. I think there are times when mechanical does beat electronic, especially when voltage isolation is needed and the switched current is greater than an amp or so.

Quote:
Originally Posted by bobc0 View Post
Also is it really the right thing to have the system cut electric power with no chance of pilot override when it thinks the batteries are empty? Shouldn't this be a choice the pilot makes?
I think you may have missed some of the features. There are warnings lights that come on if a cell goes below a voltage which gives the pilot what should be the only low fuel warning needed. If the pilot continues and actually empties the tank, then he has to expect the motor to stop. And beyond that I have given him the option to continue in about 60 second intervals to destroy the battery if he feels the situation warrants it. This level of fuel control is vary rare in regular aircraft.

Quote:
Originally Posted by bobc0 View Post
Those cellogs are great aren't they - the only issue I have is that the fault output plug/socket has always broken when I've tried to use it (I always ended up with a soldered connection...)
Thanks for the connector headsup. I am testing out the BVM-8S I got on ebay for $11 delivered (see attached pic). It has a larger display and it will be easier to weatherproof. Also, it already has bright red LED for alrams and a VERY loud beeper. It draws a little more power (24ma vs 16ma) but I think I still prefer it.

Quote:
Originally Posted by bobc0 View Post
An alternative approach would be to continue to use the RC LiPos but spend more on cellogs (see PS below...)
When you combine all the reasons I stated for not flying Zippy's anymore I did not feel that it was worth my time and effort to add CellLogs to an obsolete design and they would not have addressed a lot of my concerns.

Quote:
Originally Posted by bobc0 View Post
PS - you have, I guess 60 cycles on the batteries now - you say "just a few" of the ~400 cells are down to as low as 75% capacity; how many is just a few? If you parallel cells, won't it become more difficult to spot a low capacity one? (compared to paralleling 3 full voltage series strings) Surely you'd parallel at the cell level in order to tolerate the odd low capacity cell, rather than isolate & replace it??
Unknown # of weak cells, my guess right now is 6, there are six 8s4p packs per motor when the 3 series jumpers are removed. Even so, one bad cell in a 4p row (that is 4 cells from 4 different 4s packs) is still hard to isolate and replace. No way of telling whether you have one two or three bad cells in that 4p string until you unplug all connectors and test the cells individually. It is just long and tedious and when you do replace a cell then another weak cell could show up in that row on the next flight. We have not been overdischarging the cells, just getting shorter flight times to my 57 volt low voltage limit that we adhere to (3.56 v/cell if they are all balanced). When the PL8 chargers take 2 hours to charge when they should have charged in a hour, we know that that extra hour balancing at the end indicates a row of 8 cells has one or more weak cells in it (we charge at 8s8p). Only once have we had the PL8s start out in 'Safety' charge mode which, if I remember correctly, meant that there was a delta V of over 150mv when the charge was started. In that case I ended up replacing 4 cells in one 4p row. Even if I decided to spend the time and effort to replace the weak cells, don't forget the odd cell venting we had which concerned me even more (see pics) Puffing was almost not noticeable when this cell was removed from service after the pinhole vent was discovered.

Dale
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Old Dec 30, 2011, 02:37 PM
Dale
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Quote:
Originally Posted by olgol View Post
Dale, any concerns or complaints about the motors or controllers?
Are you planning to stay with Joby?

If there was a way to monitor ALL cells and pinpoint bad cells, in order to replace them with fresh ones, wouldn't RC hobby batteries still be a viable implementation? likely the cheapest I would guess. But the BMS cost and complexity might become very high.
No concerns about the Joby motors or JetiSPIN 300 controllers.

I do wish the Jeti had a smoother motor start but it has never failed to start the motors when commanded.

I am though looking for a controller with reverse in the air so that I can use the motors as dive brakes.

The cheapest BMS and voltage display solution is a CellLog type of device (as little as $11 per 8 cells). Even if I had this I would still stop flying the packs I have.

Dale
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